Stabilization of motor fuels



I Patented Se t. 25, 1945 f STABILIZATION OF MOTOR FUELS Elmer W. Cook, New York, N. Y., and William D. Thomas, .Ir.,v Stamford, Conn, assisnors to American Cyanamid Company, New York, N. Y a corporation of Maine No Drawing. Application November 29, 1941,

Serial No. 421,034 a 6 Claims. (01. 44-74 This invention relates to improvements in motor fuels, specifically those such as gasoline which contains gum forming constituents. More specifically;the invention is concerned with the prevention of gum formation in motor fuels by the addition thereto of a new class of gum inhibitors; namely, N,N'-dicycloaliphatic-p-phenylenedia- -mines.

It is a well known fact that motor fuels produced by cracking processes tend to deteriorate upon storage with the formation of undesirable gums. In general, the higher the cracking temperature employed in processing the gasoline the greater the tendency of it to form gums. Gas-' olines produced by the polymerization of oleflns from crackingstill gases and coal-tar benzole, frequently employed in motor fuels, produced by processes employing high temperatures also show gum-forming tendencies. The deterioration of the motor fuel is believed to be due to unsaturated bodies in the fuel which polymerize with the formation of dark colored resinous gums thus lowering the color of the motor fuel and causing the formation of hard resinous deposits on the intake manifold and valves of the engine.- It is.

'. ous aryl and alwl N,N' substituted p-phenylenediamines and mixtures thereof.

We have now discovered that N,N'-dicycloaliphatic-p-phenylenediamines, which we believe to be new compounds, may lie-prepared by a method to be presently described and that such compled to one secondary carbon atom of the substituent cycloaliphatic radical and it is to this distinction that'we ascribe the greater effectiveness of our compounds asdistinguished from those heretofore employed in gasoline as gum inhibitors.

In addition to being eflective gum inhibitors the compounds'of this invention a number of other advantages which make their use for this purpose highly desirable. The particular compounds described herein have a marked solubility in gasoline and their incorporation therein may be easily accomplished. They are, on the other hand, quite insoluble in water and since gasoline is generally stored over water they are not thereby extracted from the gasoline as frequently happens when :using water soluble gum inhibitors. The compounds of the present invention are also insoluble in alkaline solutions and are not extracted from the gasoline by residual alkalies left in the gasoline after refining operations. A further and important advantage of the compounds of the present invention is that should they be oxidized by high temperatures, compoimds pounds may be added tomotor fuels, particularly cracked gasoline, vthereby effectively stabilizing the fuel against deterioration and gum forma-,

tion.

So far as we are aware the N,N' p-phenylenedie-mine gum inhibitors heretofore employed have been of such structure that the nitrogen of the p-phenylenediamine nucleus isattached to either a primary or a tertiary carbon atom. For example, the carbon atoms of phenyl groups .are tertiary and are directly attached to the nitrogen atoms of the phenylenediaminenucleus in compounds such as N,N'-diphenyl-p-phenylenediamine. In the alkyl substituted p-phenylenediamines such as N,N'-buty1-p-phenylenediamine and N,N'-diisoamyl-p-phenylenediamine the nitrogen of p-phenylenediamine nucleus is attached to a primary carbon atom. In the compounds of the present invention each nitrogen atom ofthe p-phenylenediamine nucleus is conas N,N-diphenyl-p-phenylenedlamine would be formed which are also effective as antioxidants.

The compounds of the present invention may be prepared by mixing approximately 2 moles of a cycloaliphatie ketone with one mole of p-phenylenediamine and treating the mixture with hydrogen in the presence of a hydrogenation catalyst. The cycloaliphatic ketones which may be employed include those such as cyclohexanone: methyl cyclohexanone; dimethyl and trimethyl cyolohexanones; ethyl, propyl, butyl and amyl -mono-, diand tri-substituted cyclohexanones: cyclopentanone, methyl cyclopentanone, cycloheptanones and the like.

The reaction whereby the NN'dicycloaliphaticp-phenylenediamines of the present invention are produced may be illustrated by the following equation, using cyclohexanone as the cycloali- Dhatie ketone:

- Although it has not been definitely established a. would appear that during the course oLthis reaction a compound of the following is first obtained ranging from as little as parts of the inhibitor per million parts of gasolineto' amounts exceedin: 200 parts per million with increasingly efiectiveresults. TheNN'-dicycloaliphatic-p-phenylenediamines are effective in inhibiting. gum formation in cracked gasolines, gasoline-s produced by polymerization of olefins, in blended gasolines containing unsaturated bodies tendingto form gums and in gasolines blended with benzol, alcohols and other combustible materials. "They may also be used with conventional anti-knock compositions such as tetraethyl lead fluid and with dyestuffs and other inhibitors of various kinds.

This latter compound is easily reduced by hydrosen to yield NNdicyclohexyl-p-phenylene-diamine as illustrated above. 1 i

The catalytic reduction is carried out with one Q of the many conventional hydrogenation catalysts available such as copper chromite,- Raney nickel, nickel-copper, platinum black, palladium black, nickel-alumina, nickel, copper, nickelthoria, etc. or combinations thereof. The: reduction is carried out at temperatureapreferably ranging from 100 to 200' C; and at pressures within the range 500-2000 pounds Der square inch. The time required may vary from 1. hour up to' 10 or more hours depending upon the tem- Derature, pressure and activity of the catalyst.

In conducting this hydrogenation it is most convenient-to dissolve the reactants in an inert solvent as, for example, alcohols such as isopropyl alcohol, amyl alcohol, etc., and various ethers and hydrocarbons. An excess of the ketone itself may also be employed. I

1 The preparation of our new gum inhibitors will 1 now be illustrated in greater detail in the following example. It will be understood, of course, that this particular example is given merely for purposes of illustration and is not intended to be in limitation of our invention since as pointed out above "other cycloaliphatic ketones, hydro-- ger ation'catalysts and reaction conditions may be employedif desired. 7 a I Exam I 54 parts by weight of p-phenylenediamine and 196 parts by weight of cyclohexanone were dissolved in 116 parts by weight of isopropyl alcohol and 14 parts of copper chromite added thereto as catalyst. The reaction was carried out in a pressure autoclave at a temperature of 150-170" C. and a pressure varying from 10Q0-l670pounds per square inch over a period of 1.5 hours. After reduction the catalyst was filtered of! and-the solvent removed by evaporation. NNdicyclo-' hexyl-p-phenylenediamine remained as a pinkish-red colored oil that crystallized on standing. The crude product thus obtained had a melting point of around 55 C. and waslreadily soluble in alcohols, gasoline, benzene and other common organic solvents.-

The NN'-dicycloaliphatic-p-phenylenediamines prepared as described above may be. usedas gum inhibitors as they come directly from the hydrogenation autoclave. may be further purified by distillatlonin vacuo.-

The'NN'qdicycloaliphatie-p-pheiiylenediamines Ii I desired, however, 7 they I What we claim is:

The 'eflectiveness of our new gum inhibitors in preventing gum formation in gasoline is shown in' the following table in which the results obtained with a member of our new class of compounds is givenin comparison with the results obtained with 'n-monobutyl-p-aminophenol, a very well, known and eflective gasoline antioxidant; and the untreated gasoline alone. The gasoline employed was of the cracked typ which had been doctor sweetened. These tests were made according to the procedure prescribed for theA. S. T. M., oxygen bomb test B 525-39T recognized in the industry as a standard method of measuring the gum forming tendencies of gasoline. I

' TABLE...

' .4. s. r. M. omen bomb test 3525-391 cracked a type, doctor sweetened gasoline I concem Induction Inhibitor I tmflon P. P. M None l. 36 N-monobutyl-p-amlnophenol 121 NN'-dicyclohexyl-p-phenylenedisminc.. 60 131 1. A motor fuel containing unsaturated hydrocarbons which normally tend to develop gums,

stabilized against said' gum formation by the presence of a small amount of N,N-di-cycloaliphatic-p-Dhenylene diamine.

2. A motor fuel containing unsaturated hydrocarbonswhich normally tend to develop gums,

stabiiized'against said gum formation by the presence of small amounts of'a' N,N-di -cyclo-' hexyl-p-phenylene diamine.

3. A motor fuel containing unsaturated hydrocarbons w ch normally tend to develop gums, stabilized against said gum formation by the presence of small amounts of a N,N -di-methylcyclohexyl-p-phenylene diamine. T 1

4. A motor fuel compris n asoline containing gum-forming constituents and a small amount oi a N.N-di-cyclohexyl-pphenylene diamine.

5. A method of stabilizing gasoline which normally tendsto deteriorate and develop gums on storage which comprises adding thereto a small amount of a N,N'-di-eycloaliphatic-p phenylene diamine. I

8. A method of stabilizing gasoline which normally tends to deteriorate and -develop gums on may be employed as gum inhibitors in amounts storage which comprises adding thereto a small amount of a N,N'-dl-cyclohexyl-p-phenylene diamine. I

ELMER w.-cooK-' WILLIAM D. THOMAS, JR. 

